Peter - Yes LED 7' units - like on the plusfour would be fine aftermarket fitted. Many Landrover defenders are fitted with such. Indeed Cain @ Wolf performance sells upgraded LED headlamp units for classic Morgans.
MOT doesn't rule out LED sidelights - the only consideration is the colour of sidelights and that they work.
front position lamps ( sidelights) , the following colour of light is acceptable:
white light
predominantly white light with a blue tinge
yellow light - if combined in a yellow headlamp
